Generally, a photographic light-sensitive material is manufactured by coating at least one photographic light-sensitive layer onto one surface of a plastic film support, and further optionally by coating a magnetic recording layer, or a backing layer, onto the other surface of the support. Up to now, fiber-series polymers, represented by triacetylcellulose (hereinafter referred to as "TAC"), and polyester-series polymers, represented by polyethylene terephthalate (hereinafter referred to as "PET"), have been used for the plastic film support.
The TAC film has a problem that needs to be solved from the viewpoint of the environment, because an organic solvent is used in the course of producing the film. The TAC film also has a weak point of mechanical strength. The PET film has been widely used for sheet-like-shaped articles, such as an X-ray film, lith film, and cut film. However, when the PET film is used for a photographic support that is encased into a patrone (a magazine) in the form of a roll and in the size (width) of 35 mm or less, the same has a strong core-set curl. Therefore the PET film is not always satisfactory, because such problems as out-of-focus arise in the step of printing to a photographic printing paper. Further, with respect to a base film for a magnetic recording medium, JP-A ("JP-A" means unexamined published Japanese patent application) No. 113529/1987 discloses a proposed method for improving both the flatness of the film and the workability of handling of the film. In the method, a film is made of polyethylene naphthalate (a raw material) whose specific resistance when it is melted is in a specific range, according to an electrostatic-applied cooling process, and further the thus-obtained film is modified so that a specific formula can be satisfied by the relation between the surface roughness of the film and the thickness of the film.
In particular, recently usages of photographic light-sensitive material have expanded, and further high-speed conveyance of film at photographing and miniaturization of photographic devices have progressed. Accordingly, there is a demand for a photographic support having not only core-set curl resistance, but also mechanical strength and dimensional stability that are satisfactory for a thin film. However, this demand cannot be adequately met by the conventional TAC films and PET films. So, there is need for development of a photographic support that can meet this demand.